PTT-621

Primary objective: To evaluate the safety and tolerability of PTT-621 after single and multiple administrations of different doses in healthy subjects. Secondary objective: To evaluate the pharmacokinetic (PK) characteristics of PTT-621 after single and multiple administrations of different doses in healthy subjects. Exploratory objectives: 1) To explore the characteristics of changes in biomarker concentrations in vivo after single and multiple administrations of different doses of PTT-621 in healthy subjects; 2) To evaluate the effect of blood drug concentrations of PTT-621 on the QTc interval after single and multiple administrations of different doses in healthy subjects (C-QTc study); 3) To explore the effect of food on the pharmacokinetic characteristics of PTT-621.